Been driving my newly acquired 2000 XJ/70,000 miles for about a month now, and it's been running great, until yesterday I got my first scare.
For some tedious reasons involving airport drop off/pick up, I ended up sitting with the engine idling, perfectly smoothly, for about 20-25 minutes. I shut down the engine for about 10 to unload gear, and when I went to drive off, I could not get it started. The engine turned over, but sounded like it was choking the whole time, sputtering at a less then 200 RPM for a few seconds, and then just dying. Applying the gas did nothing, opening the hood and manually working the throttle, nothing. With that not going anywhere I stepped back and let it sit for about 5-10 minutes. Got back in, and it started right back up without so much as a sputter, and drove smoothly off to the parking garage. There was also a definite smell from under the hood, one I didn't recognize; definitely not burning oil, but no signs of any leaks anywhere or any kind of smoke visible.
No idea where to start; I cleaned the throttle body and replaced the TPS sensor a couple weeks ago (which seemed to smooth out some issues with the over drive acting a little erratic at highway speeds). I thought about doing the IAC when I get back, but I figured I'd see if I could replicate it first (which I think it will, I idled it for 10-15 minutes a few weeks ago, shut it off, and when I fired it back up a minute later the idle was strangely rough for a while, when it's normally very smooth) and see if there were any better guesses here, particularly about that smell. (Not that I can describe that effectively at all; definitely not oil, and not really very powerful, but with some kind of chemical undertone.)
Thanks

 

google HEAT SOAK

 

^^^^
This, and after that call up your nearest dealer and ask them about the intake manifold heat shield campaign. They should install the shield at no charge to you. Also, I'll be the first to congratulate you for being lucky to get such a low mileage XJ, but if it were me I wouldn't let it idle for that long. The 00-01 XJs are very allergic to overheat. In a lot of cases a single overheat episode can convert that relatively new head on your XJ to an 84lb door stop. Watch coolant level once a week.

 

Sounds indeed like a 2000 heat soak issue, doesn't it...well, better than a cracked 0331 head, to keep things positive.

 

Yeah, I've read up on the 0331 head issue. I'm hoping it's still an 'if' rather than a 'when' issue, but till then it seems like the best I can do is watch for coolant loss/temperature spikes. Thanks for the congrats as well Kalali; my old '96 ran to 240,000 miles before I had to retire it (rust) so finding one at 70k was pretty exciting. (Slightly less so after reading about the 0331, but I am staying positive.)

As far as the heat soak, I found the service bulletin which sounds exactly like what happened to me, with one unsettling aside: it mentions the misfire mostly happens in hot weather, 90 degrees plus, and it was barely over 20 out today. So I can't help but wonder what's going to happen when summer rolls around and it's 95 in middle of the city.

It looks like the previous owner did know something about it though, because there's some cheap looking wrap zip tied around Injector 3; I'll probably just give my local dealer a ring and see if they'll replace it and get it done right. And maybe if they recognize the smell.

 

Best prevention (for as far as you could do anything to prevent it) with the 0331 head is probably to make sure your cooling system in uptodate and good working order.

Regarding the heatsoak....with the temps in the engine bay, I'd reckon that ambient temps are relatively less of an issue...but not an heatsoak expert...

 

For anyone that comes across this in a search, I ended up taking the Jeep by the dealer; they actually okayed the old wrap around Injector 3, but they did also find and patch a handful of small vacuum leaks, which seems to have sorted the issue out. At any rate, the engine's idling a bit smoother in general, and I haven't had a bad start yet, so that seems to be something to watch out for.
Thanks all.

 

You have the two mini-cats in your exhaust manifold, right? Might be prudent to find out a way to clean them (no idea if this is possible). They are the source of all the extra heat that boils fuel, and cats tend to get quite hot when they're dirty.

As for why they're dirty on so few miles, the vacuum leaks are probably the culprit.